The present invention relates to a support device which supports the both ends of the shaft of a heavy rotatable object, particularly of a large-sized and heavy-weight turbine rotor for a power generator for checking and repairing them and easily achieves adjustment of horizontal levelling.
Conventionally when a turbine rotor for power generator, for example, is checked and repaired, two ends of a shaft of the turbine rotor are removed from the generator and are situated on a roller support base mounted on a base frame of a support device by means of a plurality of adjusting bolts. Moreover, such base frame has been generally installed on the floor surface not specially strengthened. Therefore, even if an accurate horizontal levelling of the roller support base is obtained previously by means of the adjusting bolts, when the turbine rotor is once placed on the roller support base, the floor surface is distorted or warped by the weight of said roller support base resulting in poor levelling. Such poor levelling or distortion of floor surface produces a considerable degree of thrust on the supporting rollers of roller support base. This thrust is enhanced by deflection of rotor shaft. Thereby, the turbine is encountered with irregular rotation including movement in the axial direction. Accordingly, not only check and repair of turbine become extremely difficult and cumbersome, but also, in extreme cases, such irregular rotation results in partial abrasion of supporting rollers or rupture of them in some cases. This makes check and repair very dangerous. Consequently, further level adjustment is essential for preventing such situation, but it has always required much difficulty followed by a great expenditure of time and labor.
The inventors of the present invention have proposed, in the Japanese patent application No. 168450/1981, a support device for checking and repairing a heavy rotatable object such as a turbine rotor providing an automatic level adjusting mechanism which simplifies the level adjustment by eliminating defects of existing support devices. Namely, such device can automatically align the axis of the heavy rotatable object with the axis of support rollers. However, such a support device for checking and repairing the heavy rotatable shaft which has the construction shown in FIG. 1, has not yet been considered perfect in such a point that it results in the movement of a turbine rotor (b) in the axial direction, although a little, when the turbine rotor is rotated for checking after the turbine rotor is placed on the roller support base (a). Such movement in the axial direction is supposed to occur due to the following causes.
Since the roller support base (a) is supported by the hemi spherical support (c), the axis of the turbine rotor (b) and the roller (d) supporting the end of the turbine rotor (b) would have ideally been parallel to each other when the turbine rotor (b) is placed on the roller support base (a). Moreover, even when the turbine rotor (b) is rotated by means of the roller (d), so long as the parallelism between the axes of the rotor (b) and the roller (d) are surely kept, any thrust load would not have been generated to thereby prevent any movement of the rotor in the axial direction. However, practically, both axes of the rotor (b) and the roller (d) become non-parallel because of some reasons, for example, indicated below.
(a) Machining error PA1 (b) Assembling error PA1 (c) Unbalance of roller support base (a) before placing the turbine rotor (b) PA1 (d) Unbalance of roller support base (a) after placing of the turbine rotor (b) or resultant deformation PA1 (e) Effect of driving force PA1 (f) Effect of friction PA1 (1) Destroying parallelism (alignment) between the axes of the turbine rotor (b) and roller (d). PA1 (2) Destroying a uniform contact pressure between the rotor (b) and roller (d) to thereby change inclination between the turbine rotor (b) and roller shaft (d) when a drive force is applied. PA1 (1) The roller support base (a) is fixed under the condition that the rotor (b) is placed on the support base (a) so that the base (a) is no longer rotated even with a driving force on a horizontal plane. PA1 (2) In this case, if the roller support base (a) is fixed by screwing, the movement can further be kept small through the adjustment by slightly rotating the roller support base (a) in accordance with direction and amount of movement of the base (a) when checked trially by rotating the turbine rotor (d).
The causes (a) to (d) are considered to bring about following phenomena.
Here, one condition (before start of operation is supposed) where the rotor (b) is only placed on the roller support base (a) (Refer to FIG. 1.). Although the horizontal levelling is a little poor as explained previously because of above-listed causes, the system as a whole is balanced as shown in FIG. 2. However, this condition does not guarantee that a pressure between the turbine rotor (b) and roller (d) is uniformly distributed in along the axial direction. Rather, the pressure is considered to be inwardly (blade side) or outwardly deniated. To be more in detail, if the inner pressure of one roller (d) of the roller support base (a) in the driving side is, for example, high, a resultant pressure at the inside of the other roller (d) also becomes high. Accordingly, the moments at the center of the hemi spherical support mechanism (c) must be mutually cancelled.
When a driving force is applied under this condition, a larger tangent force is transmitted in the high pressure side and thereby a reacting force resulting from the turbine rotor (b) generates unbalanced moments at the center of hemi spherical support mechanism. As a result, the roller support base (a) generates rotating deflection in the direction of such moment as shown in FIG. 3. If a gradient is thus generated between the axis of the turbine rotor (b) and the axis of the roller (d), the pressure and the tangent force are redistributed, to thereby balance the moments at the center of the hemi spherical support mechanism (c). When the turbine rotor is rotating in the condition as shown in FIG. 3, the turbine rotor (b) moves in the axial direction. If it is rotated reversely, a tangent force is generated reversely, resulting in a rotating deflection directed to the roller support base (a). Therefore, the turbine rotor (b) also moves in the same direction as explained above.
If the movement is considered to occur in the axial direction because of the reason described above, the roller support base (a) must rotate only a little in such a moment when the turbine rotor (b) is driven.
From the above observation and analysis, following measures are considered effective for making such movement in the axial direction as small as possible.
The present invention has been derived from such findings and experiences and intended to provide a support device for checking and repairing a heavy rotatable object which further simplifies the levelling or the alignment and ensures, a more accurate and safer check and repair by eliminating the movement in the axial direction of turbine rotor which has been generated by driving the turbine rotor in the existing system.
In summary, the present invention relates to a support device for checking and repairing a heavy rotatable object, wherein such device comprises a pair of self-aligning support structures for rotatably supporting both ends of the heavy rotatable object. In each support structrue, a roller support base supporting rotatably the end of the shaft of the heavy rotatable object is supported on an adjustable surface plate of the base frame by means of a hemi spherical support mechanism, and moreover a jig for adjusting the horizontal rotating position of the roller support base around the vertical axis of a hemi spherical support mechanism is mounted in the periphery of an adjustable surface plate.